Sharia4UK is a group closely associated with the banned extremist groups al-Muhajiroun, Islam4UK, and Muslims against Crusades, formerly headed by the preachers Omar Bakri Mohammed and Anjem Choudary.
In a French video a British man can be seen speaking in English in front of a banner proclaiming ?Islam pour la France? at a rally for the ?defence of Islam.?
In another section of the film, a French man can be heard translating the speeches into English.
Sources told the Daily Telegraph that French investigators had not alerted them to concerns about the brothers or potential links between the French group and extremists in the UK.
Scotland Yard referred inquiries to French investigators.
Mr Choudary said he did not know the two men. He said he had been invited to the demonstration in Paris but had not been able to attend because he was banned from France.
He said that some of his students had attended but added that Forsane Alizza was not affiliated with him but with a group he had given talks for in Belgium.
Mr Choudary said Merah?s attack was ?not verifiable? and added: ?I?m not going to judge this individual? but he said that ?shooting someone in the head, it is completely unacceptable.?
Forsane Alizza (FA) is led by a young French Muslim called Mohamed Achamlane, and has between 30 and 100 official members, according to the International Centre for the Study of Radicalisation (ICSR) at King?s College, London.
?The group appears to be part of a loosely connected European network of extremist Islamists who share the same ideology and use similar tactics,? according to Peter Neumann of the ICSR.
Its own website says that FA is a fundamentalist Salafi organisation with the primary objectives of proselytising for jihad [holy war] and the establishment of a caliphate [Muslim state] and ?support[ing] the mujahideen [holy fighters] everywhere.?
They disavow democratic systems and elections and proclaim that their principal targets are the French military, Jewish institutions and Israel, and perceived anti-Muslim prejudice.
Mr Neumann of the ICSR said it was not ?formally structured? and probably had many more sympathisers, with nearly 2,000 supporters on Facebook and 400 followers on Twitter.
The group has a significant YouTube presence, with at least 26 well produced videos and a video-sharing site Dailymotion, on which FA has posted 75 videos.
Its promotional videos feature paintballing exercises and combat training, ostensibly for the purposes of self-defence.
In January 2012, FA was banned by French Interior Ministry for inciting racial hatred but since then, the group has re-formed on the internet, establishing the Force de Defense Musulmane sur Internet [Online Muslim Defence Force].
Following its ban, Achamlane warned that ?armed struggle is possible? should French society become more hostile to Islam.
Mohamed, 23, shot dead three soldiers in Toulouse and Montauban last week, then gunned down a rabbi and three children at a Jewish school in Toulouse on Monday.
He died in a hail of gunfire whileleaping from a window after a 32-hour siege at his flat ended on Thursday.
Both brothers are thought to have been members of radical Islamic groups in Toulouse.
Mohamed claimed to be linked to al-Qaeda and traveled to Afghanistan where he was detained in Kandahar, apparently trying to plant roadside bombs, in 2008 and sent back to France.
French officials have said there is little evidence to back up the claims but Mohamed had been on a terrorist watch list since the incident in 2008.
Francois Fillon, the French prime minister, defended the state?s security services, insisting French police had no grounds to detain Merah before he went on his killing rampage.
He told French radio: ?Intelligence agents had surveilled him long enough to come to the conclusion that there was no element, no indication, that this was a dangerous man who would one day pass from words to acts.
?Belonging to a Salafist organisation is not an offense in and of itself. We cannot mix up religious fundamentalism with terrorism, even if we know there are elements that unite them.?